In this research, using the Modified Compression Field Theory (MCFT), a new model is proposed to predict the behavior of reinforced concrete coupling beams. The model is able to consider the effects of shear and axial forces and bending moment, simultaneously. The proposed model includes a nonlinear shear spring, an axial spring and some nonlinear springs for considering bending deformations. In the experimental part of the research, six specimens with different reinforcing layouts were manufactured and tested. In order to consider the constraining effect of slab diaphragms, three specimens were constrained, axially. The results of the proposed model were compared with the test results reported by other researchers. Good agreement was obtained between the test results and calculated values. The test results of the axially constrained specimens show that axial rigidity may change the behavior of coupling beams, considerably.